Navigation instrument



Dem 27, 1949 C, w, sTRAw l v2,492,718

NAVIGATION INSTRUMENT Filled March 22, 1945 fro 5 o a' 'n I r W.

l SGSEFIU f' "arf extra 'IIIIIIIIIIIIIIIIIIII I Imvezzaz Clarence Siraw /4 ,d I nl r Y 'y diarnegs Patented Dec. 27, 1949 lUNITED"S-I'I`ATl':'.S PATENT OFFICE NAVIGATION INSTRUMENT Clarence W. Straw, Hill, N. H.

Application Mar. 22, 1945, Serial No. 584,180

6 Claims.

My present invention relates to a navigationv instrument particularly adapted for use in navigating smaller aircraft.

Considerable difficulty is commonly experienced in navigating such aircraft and this is due to several factors, such as their lightness, the limited number of instruments with which they are equipped, and the necessity of each pilot doing his own navigating.

As illustrative of such difficulties, it will be helpful to consider the manner in which maps are widely used by the pilots of small airplanes. A pilot draws on his map a line indicating the line of flight between air fields. The map is then folded to be more compact and placed where he may consult it from time to time to make such corrections in his course as appear to be necessary based on a comparison of his observations with the course marked on his map. This procedure is objectionable in that the map slips from its place or becomes unfolded and because it is diicultzto be at all accurate in determining the extent to which a pilot is'off his course by comparing his observations with the marked course on the map.

In accordance with my invention, I provide an instrument comprising an elongated base of transparent stock having straight parallel sides and carrying a clamping member at each of its ends so that the map and the instrument may be clamped together in desired relation.' The base has, adjacent one edge, a series of transverse graduations of the same scale as the scale of the map, a center line, and a marker disposed at right angles to the center line and transversely alined with the rst graduations of the series.

A slide of transparent stock is mounted on the base and it has a -centrally disposed marker registrable with the marker on the base. The slide also has at least one transversely disposed set of graduations spaced from the marker on the slide a distance equal to a predetermined number of graduations of the series thereof with which the base is provided. The transversely disposed set of graduations may be an arcuate scale readable in terms of degrees to the right or to the left of the base center line or it may be a scale readable in terms of miles to the right and to the left of said center line. Preferably, the slide has both scales to afford to the pilot the advantages of each type.

With such an instrument, the pilot merely folds the map to the desired length and clamps the map to the instrument with the marker on 66 the base over the point of take-off and the base center line extending to his destination. He then positions the slide with its marker in registry with the base marker.

It will be apparent that the pilot is relatively familiar with the terrain either within a few miles of the air field from which he is taking off or that he can readily find out certain easily identiiied objects in its vicinity. In the use of the instrument, he selects an object or objects substantially the same distance from the air field as the distance between the marker on the slide and one of the slide scales.

In flight, the pilot follows the course indicated by the center line of the base. When he observes one or more of the selected objects, he knows that he has flown a predetermined number of miles and he knows the time required by that part of his flight. By selecting an identiliable point which he is over and locating that point on the map through his instrument, he immediately knows either in terms or degrees or miles the extent to which he is off course and can make such corrections as appear to be necessary to bring him back on course. By advancing the slide along the base, the pilot is easily able to maintain a continuous check on his course so that instruments in accordance with my invention are well adapted to overcome the difficulties o'f navigating small aircraft.

In the accompanying drawings, I have shown an illustrative embodiment of my invention from which its novel features and advantages will be l readily apparent. In the drawings:

Fig. 1 shows, in plan view, an instrument in accordance with my invention, clamped to an indicated map. Y

Figs. 2 and 3 are sections along the lines 2-2 and 3-3, respectively, of Fig. 1.

Fig. 4 is a plan View of the slide.

Fig. 5 is a section along the lines 5-5, of Fig. 4, and

Fig. 6 is a fragmentary plan View of the base.

A navigation instrument in accordance with my invention consists of a base 5 of transparent stock and a slide generally indicated at 6.

The base 5 is elongated and has straight parallel sides adjacent one of which there is a series of transversely disposed graduations establishing a scale 1. The series of graduations of the scale 1 are of the same scale as that of the map, indicated at 8. The base 5 has a center line 9 and a marker I0 disposed at right angles to the center line 9 and transversely alined with the first orr zero graduatons of the scale l. I have shown threaded on each of the elements I3 to permit the plates I2 to be adjusted into and out of map clamping relation to the base 5.

The slide 6 preferably comprises a member.. I8 of transparent stock slightly wider than the Ibase and to its margins I attach by; x11-.earns of.' screws indicated at I9 side pieces 20 each having, a pair of spaced projections 2iv entrant of slideways 22 in the base 5. The slideways 22 are preferably Ves-haped. At 23 If' have indicated a spring cut away at itsends tolr receive the projections ZI?. In the assembled instrument, movement of the slide 6 is limited by the nuts- I-1.

' I' providethef member I8 with a marker 24 registrable-withthemarkeri'llcn thebase 5; The mar-kerr 24- isV preferably the 'rst of? a series of graduations establishing ascale 25 in alinementwith the center line 9` of the base 5e and corre--Y spendingV tov a predetermined number ozgradh uations ofithe scale'l The scale 25" comprises; in the embodiment of' my invention shown in-the-drawings, graduations equivalent to-miles onthesca'le: '.1 or on the map 8. Attheequivalent-of l=5 miles on the scale 25;, l? provide a' scale- 261, arcuate with respect tothemarker 2li andvreadable inA terms of degrees tothe right or tothe lef-t relative to the scale Atthe eouiivalent` oi 2G miles on thescale 25 I-- provide a` second* transverse scale 2:1 readable inA terms off miles tothe right or lef-t off the sca-le 25. At 28- and 2@ If have indicated as by arrows'- orlike marginal'v indicia the zero and 15 mile graduaticns of the centrally dis-posed scale 25a The graduations of'4 the scal'e 25 are preferably inl t-he form of dotsv in order to` permit them tov be easily` distinguished from the center line` orr the base-5;

With the` instrument irr accordance with my invention, the pilot merely-V folds` the map it sothatit may be clamped to the instrument with the marker Iover airv iiel'd lromwhich-he-is taking off and thecenter-line 9 extending to-the air eld of destination indicatedat 3+. Hethen positions theslide tv relativeto thebase 5 to-bri'ng t-he mar-ker 241in@registrywithA themarker- H11.`

The pilot, before taking off from. thel airrel'dy SWfamiliarizes himseli with some easilyfidentiiied point or points known to bein anY areain the general direction of his courseA andz substantially the distancefrom-theaireldlas-is indicatedby the distance between the marker 24 and whicheverof' the scales 26- and; 2'11 he prefers' to select, generally the; scale 2E. He then flies and checks his time untilL he is over the area ofthe selected point; For example, he may rind' himself over the point 32' in that area and by'checki'ng that pointy onY the map 8, through the instrument,` he can determine hisoff` course positionin terms of both degreesan'dmiles and can make appropriate corrections in his course in accordance with his observations. The slide Ii' may thenbe re-positionedto bringitsmarker Zin'transverse aline;-

ment' with that.. identified` pointV and, the course may again be veried after iiying a predetermined 4 number of miles, with such adjustments as his time check indicates, on his corrected course.

From the foregoing, it will be apparent that my instruments are simple in construction and easy to use with the result that accurate navigation of light aircraft is much simplified.

What I therefore claim and desire to secure by Letters Patent is:

l. A navigation. instrument for aircraft coman. elongated transparent base to be disposed over a map, said base having straight -parallelisicles la pair of spaced map clamping means to engage and clamp the map :against the under suraceroff the base, a series of transverse graduatons establishing la scale adjacent one side with each graduation representing a predetermined distance 'onsy the scale of the map, a center line and a marker on said center line transversely iali'ned with the rst graduation of the scale, and a slide of transparent stock on the base, `said map clampingmeansnconstitutingstopslimiting'movementof said sliderelfatitze toisaid` base, said slidev having a marker and a transverse. scalezspaced from the marker-on the slide a. distance equal to a predetermined? number offunits of: the scale. 0n thehbase said? instrumentzbeing disposable, on. the mapfwith the marker ot thebase over the takeoifI andi with the center' line extending to the destination and having am operative position in whichthe marker oi'theslide is positioned with referencetm the marker on. the.. base so. that the marker -on the slideL isv transversely.y alined withv the rfstv graduation or?v the scale on theibase so thatzbyselectingia known pointon. the ground belowJ the aircraftiir an area. known to be; of substantially thefsamedistancefrom the take-off as' itrdi'oat'edy by'thealbcatiorr offtheuscale. onthe slide with reference to. the slidemarker, the location thatzpoint' on` the map. as viewed' through the scale on the slide revealsthe ofii course position otticoaircraft;

2'; The instrumentA ofi` claim 1;. in which the clampingf meansy are located at each end of. the base andi each. of the clamping means comprises a plate, a threaded element and' a lpair of pins om the plate, and. theibase has' an` aperture for the element and.' af pair ot recessesv for the pins, andi a. nutI threaded on. the; element: adjustably assembles: the clamping means to the base.

2 A navigation instrument;4 for aircraft comprising Ian elongated transparent; base` to be disposed. overf a map ande having straight parallel' sides; a.. series. ofiT transverse. graduations adj acont' one-isidewitlreach. graduation representing a predetermined; distance on the'soale ofthe map, la" centerline,A atransparentmember having a centrally disposed series of graduations with. each graduation. representing predetermined distance; on. the scale: of:v the man fwithY one of said graduations constitutingra marker; and a transversely-2f' disposed scale spaced: from said marker, and means slidably connecting said member to haseaso that in any-of its positions onv said base its;y centrally disposedseriesY or graduations iri;.registry with a part lof saidzcenter line so that-.whensaid instrument" isidispo'sed. on the map with'` the; center line extending through a known pointthereon tothe. destination and the marker onatheimemben is in; registry with; that point, a known. point on; the' ground belowt'he aircraft of substantially the-same distancefrom said known point on the map iandaosubstantially thesame distance therefrom asv indicatedby.l the location othascale onzthe member reveals, when-viewed on the. map;A through the instrument, the o course position of the aircraft.

4. The instrument of claim 3 in which the center line on the base has a marker with which the marker on the member is registerable and which is transversely alined ywith the first graduation of the series thereof yon the base.

5. The instrument of claim 3 in which the transversely disposed scale on the member is la. series of grad-uations arcuateiy disposed with reference to the marker on that member.

6. The instrument of claim 3 in which the tnansversely disposed scale on the member is a series of graduations of the same scale as the map.

CLARENCE W. STRAW.

REFERENCES CITED The following references are of record in the file of this patent:

UNITED STATES PATENTS 

